Timetrigger not firing backgroundtask UWP

Question

I have the same problem as this guy over here: UWP Timetrigger not working but I can't comment the question because my reputation is not high enough, so I'm creating a new question.

As I said, I have the same problem. I registered the background task, but nothing happens. My background task is located in a seperate project (Runtime Component). So that's not the problem. This is the method I made to register the task:

public static BackgroundTaskRegistration Register(string name, string taskEntryPoint, IBackgroundTrigger trigger, IBackgroundCondition condition)
    {
        var foundTask = BackgroundTaskRegistration.AllTasks.FirstOrDefault(x => x.Value.Name == name);
        if (foundTask.Value != null)
            return (BackgroundTaskRegistration)foundTask.Value;

        var builder = new BackgroundTaskBuilder();
        builder.Name = name;
        builder.TaskEntryPoint = taskEntryPoint;
        builder.SetTrigger(trigger);
        if (condition != null)
            builder.AddCondition(condition);

        return builder.Register();
    }

and this is how I call it:

BackgroundTaskRegister.Register(nameof(NotificationTask), $"Epguides.Background.{_backgroundTaskName}", new TimeTrigger(30, true), null);

When I debug my application and use Lifecycle Events in Visual studio to test my background task, everything works fine. So the problem is not the task.

When I inspect the BackgroundTaskRegistration result I see that the property trigger is null. on the MSDN page of BackgroundTaskRegistration.Trigger it says the following

This is not intended for use in your code. For all unsupported trigger types, the value returned by this property is null.

So from what I understand is that TimeTrigger is an unsupported trigger type, because Trigger is null.

This is what is declared in the manifest file

Is there someone that can explain why it is not working. I'm using version 10.0.10586

Answer 1

1. You can confirm that the your task is registered or not by using powershell. Open powershell with administrative rights, and run 'Get-AppBackgroundTask'. All of registered tasks are listed. If you can't find your task from the list, there are some problems at registration.

2. Have you add the background task project as a reference to your main app?

3. Have you call the BackgroundExecutionManager.RequestAccessAsync()? You should call it before registering, from UI thread.

4. I have a sample app of background task with timetrigger on the store. It's hidden from storefront and search, but you can download it from following link:

https://www.microsoft.com/store/p/ddlgbgtasktrial/9nblggh4s785

This app regist a simple background task with 15min interval timetrigger. This task just output the debugmessage to the logfile. The app shows a log. If it works well, you can see the debug output with about 15min intervals.

I've confirmed that the app works with Win10 desktop 10586.494 and mobile 14393.0.

Answer 2

I had exactly same problem with TimeTrigger (Application trigger was working without any issues) and I followed every step from MSDN regarding BackgroundTask in UWP. But ONLY below "magic line" helped me to solve - BIG THANKS to @Canol Gökel for his reply in comments (I think it deserve separate answer):

BackgroundExecutionManager.RemoveAccess(); // This is the magic line!
var backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();

Time trigger is part of UWP background task sample (Scenario 4) which was working for me. But this line is not used there at all. Instead it is used in NFC sample during check if application was updated:

    private static async Task<bool> DoBackgroundRequestAccess()
    {
        String appVersion = String.Format("{0}.{1}.{2}.{3}",
                Package.Current.Id.Version.Build,
                Package.Current.Id.Version.Major,
                Package.Current.Id.Version.Minor,
                Package.Current.Id.Version.Revision);

        if ((string)Windows.Storage.ApplicationData.Current.LocalSettings.Values["AppVersion"] != appVersion)
        {
            // Our app has been updated
            Windows.Storage.ApplicationData.Current.LocalSettings.Values["AppVersion"] = appVersion;

            // Call RemoveAccess
            BackgroundExecutionManager.RemoveAccess();
        }

        BackgroundAccessStatus status = await BackgroundExecutionManager.RequestAccessAsync();

        return status == BackgroundAccessStatus.AlwaysAllowed
            || status == BackgroundAccessStatus.AllowedSubjectToSystemPolicy;
    }